Magnetically controlled mercury wetted switch and electrical relay incorporating such a switch

ABSTRACT

A mercury wetted switch, controlled by a magnetic field produced from a discret semiconductor encapsulating box or case, whose base has a double or so-called &#34;common&#34; electrode and at least one other insulated electrode. A moving plate engages in fork-like manner in the double electrode and bears against another electrode. The liquid wetting the contacts forms a liquid hinge for the plate on the double electrode. 
     Application to electrical relays, particularly for professional equipment and telecommunications.

BACKGROUND OF THE INVENTION

The invention relates to a magnetically controlled switch with contactswetted by a conductive liquid.

Switches with contacts wetted by a conductive liquid, generally in theform of mercury or a mercury amalgam are known in the art and arenormally called mercury wetted switches. This category of electricalswitches is generally constituted by a system of associated plates,whereof at least one has a certain flexibility. They are sealed into aglass envelope into which has been introduced an adequate quantity ofmercury to wet the plates. The main advantage of this type of switch isthat it offer a very good electrical contact, without impairing thecontacting surfaces because they are wetted by mercury. However, itfrequently has the disadvantage of using methods for sealing the platesin the glass envelope which are complicated and onerous, while leadingto the contamination of the electrical contacts during the sealingwithin the glass. Moreover, it is necessary to machine the flexibleplates and the dimensions required by the plates make the overall sizeof the switch relatively large. Finally the fact that the plates aresealed within an envelope calls for a setting or adjustment,particularly of the sensitivity. When in use the mercury vaporizesduring breaks on the contacts and is partly deposited within the glassenvelope, so that the amount of mercury on the contacts is reduced, sothat a mercury reserve must be maintained within the envelope. As aresult of this mercury reserve the operation of the switch in theenvelope must be ensured in a clearly defined position in such a waythat the mercury reserve present does not short-circuit the contacts.

Thus, an adaptation of the existing techniques of mercury wettedswitches requires:

a design permitting the use of the switch in such a way that it isposition-independent, particularly with respect to the vertical of thelocation;

a simplification of manufacturing conditions involving more particularlythe elimination of contact contamination during the sealing operation,the elimination of flexible plates which need to be machined and theelimination of the actual sealing operation which is always difficult onever-smaller devices;

a reduction in the switch dimensions in such a way that it is possibleto miniaturize the relay and automatically fit its components by meansof an automatic machine.

BRIEF SUMMARY OF THE INVENTION

The only point in common between the mercury wetted switch according tothe invention and switches having flexible plates is the contact openingor closing function ensured by the mercury wetted surfaces. It obviatesthe disadvantages of manufacturing switches in a glass envelope and ofadjustment during use. It utilizes:

a metal plate in which the flexibility is of no significance because itis movable, without requiring the use of mechanical hinges as has beendone in certain known switches;

a liquid hinge constituted by mercury or any other conductive liquidwhich also ensures electrical contact between the moving plate and thepivot axis constituted by two pins between which is slid one end of theplate;

two electrical contacts, generally called the make and break contacts,formed by two pins against which abut the end of the plate opposite tothat located in the liquid hinge.

Thus, the present invention relates to a magnetically controlled mercurywetted switch which comprises electrodes made from a ferromagneticmaterial, whose surfaces are wetted by an electricity-conducting liquid,a first electrode constituting the so-called "common" contact and atleast one other electrode, wherein the passage of electrical currentfrom the first electrode to another electrode is ensured by at least oneelongated ferromagnetic material plate which moves about a liquid hingeformed by capillarity by the conductive liquid wetting the "common"electrode and the plate surface, which also bears against anotherelectrode and is held against the latter by the action of surfacetension forces, the position of the switch in space being unimportant.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is described in greater detail hereinafter relative to twonon-limmitative embodiments of the mercury wetted switch according tothe invention and with reference to the attached drawings, wherein show:

FIG. 1 a prior art mercury wetted switch.

FIG. 2 the basic components of the switch according to the invention,the auxiliary parts being omitted to simplify the drawing.

FIG. 3 a relay using the mercury wetted switch according to theinvention in a first embodiment.

FIG. 4 the basic components of the switch according to the invention ina second embodiment.

FIG. 5 a first improvement of the invention.

FIG. 6 a second improvement of the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 shows a mercury wetted switch as an example of the many typesknown from the prior art. The body 1 of said switch constitutes thecommon contact. Through its entire length runs a cylindrical channel andthe two ends thereof are blocked by two contact pieces 2 and 3, whichare held in the body and insulated by means of rings 4 or a glass-metalseal. The moving part 5 is constituted by a cylinder which moves withinthe perforated channel in body 1 under the action of a magnetic field.Electrical contact is ensured by a quantity of mercury 6 which isadequate for establishing a film between the moving part 5 and body 1and for establishing contact by capillarity with one of the two endcontacts 2 or 3. When the moving part moves and leaves one contact tocome into bearing contact with the other contact, the mercury filmbreaks on the first contact and is established with respect to thesecond contact, because there is not sufficient mercury for electricalcontact to take place at both ends of the moving part. A magnet orcontrol coil system 7 ensures the displacements of the moving partwithin the switch body.

This type of switch effectively ensures wetted contacts and operatesindependently of its position. However, a very precise machining isnecessary in order to ensure that the mercury film providing the contactbetween moving part 5 and body 1 is sufficiently thick to meet thecapillarity requirements. However, under these conditions the movingpart is relatively frequently blocked and in addition this method isonerous.

FIG. 2 shows a switch according to the invention. The drawing only showsthe parts necessary to provide an understanding of its operation.

At least four electrodes 9, 10, 11 and 12 are sealed in a base 8. Themoving part is constituted by a plate 13 held between wetted electrodesby a conductive liquid. The electrodes 9 and 10 are sufficiently closeto one another to enable the plate to be slid between the two electrodesand held by the mercury which wets electrodes 9 and 10 and the surfaceof the plate, thus constituting a liquid hinge 14. The two otherelectrodes 11 and 12 are positioned in such a way that when the movingplate 13 moves it strikes against the electrode 11 or against electrode12. The four electrodes 9, 10, 11 and 12 are sealed in base 8 by meansof electrically insulating passages 15, generally constituted by glasspowder-based fritting.

The length of moving plate 13 slightly exceeds the center-to-centerdistance between electrodes 9 and 10 on the one hand and 11 and 12 onthe other. It is not mechanically connected to the electrodes and isonly held by the surface tension forces of the conductive liquid, at oneof its ends by liquid hinge 14 and at the other end by a surface tensionwith the electrode against which it bears. Under the action of themagnetic control field the plate is automatically recentered withrespect to the electrodes of the switch.

FIG. 2 shows a cylindrical base 8 formed by the base of a discreetsemiconductor box. However, the elongated base of a quartz encapsulatingbox is also suitable for constructing the switch according to theinvention. It is important for the base to be formed from a materialpermitting on the one hand glass/metal sealing and on the other it mustbe ferromagnetic. Thus, the electrodes are sealed through the base ininsulating glass beads and traverse the base in such a way that one oftheir ends is accessible when the relay is terminated and confinedbeneath a cover.

The four electrodes are also made from a ferromagnetic material in sucha way that the control field can be reclosed in accordance with thegeneral operation of magnetically controlled switches. The cover whichis welded to the base when the relay is finished and adjusted is madefrom a non-magnetic material.

Inter alia this type of switch has two advantages. It is firstlypossible to reach the electrodes in order to mechanically regulate them,particularly in view of the sensitivity required for the switch.Secondly it is possible to only chemically treat the part within therelay before welding the cover with a view to a subsequent treatmentwhich takes place when the mercury has been introduced into the switch.Thus, a mercury wetted switch undergoes a thermal treatment whichcompletes its manufacture. When the cover is sealed by electricalwelding to the base, a quantity of mercury is introduced into the switchwhich has previously been mechanically treated and a pressurized gas isalso introduced into the thus formed sealed enclosure in order toprevent arc formation. The hollow electrode which has served as anexhaust tube for introducing mercury and gas is then closed. The switchis then heated so as to form an amalgam between the mercury and thematerial deposited on the surface of the electrodes and the movingplate.

The structure of this mercury wetted switch ensures that the contactsare not contaminated during sealing, because there is no longer anyglass envelope heating. Moreover, as the cover is made from a metal, themercury can wet its inner surface, so that the switch has a considerablemercury reserve with respect to the working contact surfaces, the coverrecovering the mercury which vaporizes during contact breaks, saidmercury being recycled. Finally, unlike the known mercury wettedswitches, the switch according to the invention operates without anyjamming, because the moving plate no longer rubs against a cylindricalbody or between two ceramic supports.

FIG. 2 deliberately does not show the small magnet used for polarizingthe plate and contacts, while the cover has been removed, all this withthe aim of making it easier to understand the drawing. A reversingswitch with six fixed contacts is based on the same operating principleand represents the optical doubling of the switch of FIG. 2.

In this case electrodes 9 and 10 on which the liquid hinge 14 is formedare sealed in the center of base 8 and hold the moving plate 13, whichpivots in its center instead of around one of its ends. Four electrodesare arranged symmetrically, electrodes 11 and 12 on one side of therotation axis and 11' and 12' on the other side thereof. They are sealedand regulated in such a way that in a first position the plate isapplied to two electrodes, and in a second position to two otherelectrodes. In the case of the present reversing switch it may bepreferable for the electrodes which serve as a hinge not to be connectedto the electrical mains.

FIG. 3 shows a sectional view of a finished switch according to theinvention. There is once again a base 8 traversed by electrodes 9 and 10on the one hand and 11 and 12 on the other, sealed into base 8 by glassbeads 15. At least one of these electrodes 12, FIG. 3 can be hollow inorder to permit the introduction of the mercury and the filling gas. Themoving plate 13 is held by a liquid mercury hinge 14. A control coil 16is positioned beneath the switch and the field of this coil is closedagain on itself via electrodes 9 and 10 on the one hand and 10 and 11 onthe other. The non-magnetic cover 17 is sealed by electrical welding tobase 8 and a magnet 18, which is partly hidden in the drawing, polarizesthe contacts. The assembly formed by the mercury wetted switch and themoving plates polarized by a magnet inside or outside the cover andcontrolled by a coil 16 constitutes a relay.

This relay can also be operated without a magnet 18 by means of twocoils, each attracting plate 13 in one position.

FIG. 4 shows the switch according to the invention in a secondembodiment.

In this embodiment the switch still has a base 8 to which are welded twopins constituting the hinge about which the moving plate pivots. The twopins 19 and 20 are then welded and positioned in accordance with a planeparallel to the upper plane of the base. The moving plate 13 pivotsaround a liquid hinge 14, which is no longer perpendicular to the upperplane of the base and is instead parallel thereto. The two electrodes 21and 22 are bent so as to ensure contact with moving plate 13 inaccordance with generatrixes which are also parallel to the upper faceof the base. The make and break electrodes 21 and 22 are also sealedinto the base by means of the glass beads 15. The polarizing magnet 18is held by any appropriate means, but can be fixed to the base by awelded pin 18a. Electrodes 21 and 22 traverse the base, which also has athird output pin 23 electrically corresponding to the contacts with theplate, i.e. the common contact. Moving plate 13 is maintained in spaceby the capillarity of the liquid hinge 14.

FIG. 5 shows a first improvement of the invention providing shock orimpact stabilization for the plate. It has been stated hereinbefore thatthe plate, which is not mechanically connected to the electrodes, isautomatically recentered by the magnetic control field of the switch.However, in order to comply with certain equipment requirements, e.g.shock resistance, the invention provides a first anti-shock improvement.In FIG. 5 plate 13 is shown between two electrodes 9 and 10 againstwhich it is held by a liquid hinge 14. On one side of the electrodes theplate is bent at 24 preventing it from sliding in a first direction.Moreover, on the other side of the electrodes it has a member 25 whichis turned down substantially perpendicular to the moving plate. Parts 24and 25 of the plate are spaced in such a way that it retains a degree offreedom adequate for holding the same, without however requiring anyadjustment of the assembly.

FIG. 6 shows a second improvement of the invention which balances theplate if shocks or impacts occur during operation.

One of the problems with conventional mercury wetted switches is theirsensitivity to shocks and impacts during operation as a result of theasymmetry of the plates. In the mercury wetted switch according to theinvention most of the plate is located on the same side of the liquidhinge. The improvement of FIG. 6 consists of balancing the mass of plate13 pivoting about a liquid hinge 14 by a moulded, welded or remeltedmass 26 located on the other side of hinge 14 with respect to the mainmass of plate 13. This improvement has an advantageous effect withrespect to shocks occurring during operation, because the mass 26prevents plate 13 from sliding between electrodes 19 and 20.

Hereinbefore the liquid hinge 14 has been described as being formed bycapillarity of the conductive liquid between two electrodes 9 and 10 or19 and 20, depending on the drawings. Thus, the liquid hinge 14 can beformed between the plate on the one hand and a single electrodeconstituted either by a pin which is curved on to itself in the form ofa hairpin or a part machined into the shape of a fork.

The switch according to the invention and the relay produced from thisswitch have a certain number of advantages, including its very highsensitivity, i.e. its operation under a low current, while beinginsensitive to impacts and to the operating position. Moreover, it ispointed out that it is easy to manufacture, without requiring highlevels of precision in the construction of parts. The setting oradjustment of the electrodes or the sensitivity can be performed on theswitch during manufacture before sealing it in a tightly sealed box orcase. It is formed from base members, which are readily available,because they are of the type used in semiconductor devices. Such amercury wetted switch and such a relay can be widely used in industryand particularly in the telephone industry and in the construction ofelectronic stations.

What is claimed is:
 1. A switch comprising: a base having a planarsurface, a cover placed over said planar surface so as to definetherewith a closed space, a plurality of electrodes of ferro-magneticmaterial passing through said base and surface into said space,electrically insulating glass/metal welds surrounding said electrodes insaid base to seal said electrodes with respect thereto, the planarsurface of said base and the interior surface of said cover and thesurfaces of said electrodes inside said space being wetted by anelectrically conducting liquid, said welds being the only surfaces ofsaid space not wetted by said liquid, one of said plurality ofelectrodes forming a common contact, at least one elongated plate offerro-magnetic material arranged in said space and extendingsubstantially perpendicular to said planar surface of said base, saidplate being movable about a liquid hinge formed by capillarity by theconductive liquid wetting the common electrode and plate surface, saidplate being adapted to bear against said at least one other electrodeand to be held thereagainst by surface tension so that electricalcurrent may pass from said common electrode to said at least one otherelectrode.
 2. A switch according to claim 1, comprising two metalmembers provided adjacent the plate at the liquid hinge which are turneddown perpendicular to the planar surface and on either side of thecommon electrode, and whose function it is to make the switchinsensitive to shocks and impacts, the plate also being adapted to beautomatically recentered on the electrodes by a magnetic control fieldduring operation.
 3. A switch according to claim 1, wherein the platehas a counterweight at its end located on the side of the liquid hingeaway from the other electrodes.
 4. A switch according to claim 1,wherein at least one of the electrodes is constituted by a tube forintroducing conductive liquid and pressurized gas into said space.
 5. Aswitch according to claim 1, wherein said hinge extends perpendicularlyto said planar surface.
 6. A switch according to claim 1, wherein saidhinge extends parallel to said planar surface.
 7. A switch according toclaim 1, wherein said base is essentially cylindrical and of magneticmaterial, said core being of non-magnetic material, said liquid ismercury, and said one electrode is composed of two pins between whichsaid plate extends, with mercury forming said hinge.
 8. A switchaccording to any one of claims 1 to 7, in combination with an electricalrelay, having a contact polarizing magnet, and at least one magneticcontrol coil.
 9. The combination according to claim 8, wherein thepolarizing magnet is a magnetic control coil.